This invention relates to an improved carbonaceous heat source and to the conversion of gaseous by-products, such as carbon monoxide, produced by the combustion of the carbonaceous heat source and methods to make such a heat source. The methods and heat source of this invention are particularly suitable for use in a smoking article such as that described in U.S. Pat. No. 4,991,606 commonly assigned herewith. The heat sources of this invention comprise a carbonaceous material and smaller amounts on a weight basis of a metal oxide. The heat sources of this invention have low ignition temperatures and high combustion temperatures. Upon combustion, the metal oxide component of the heat source chemically converts substantially all of the carbon monoxide to a benign substance.
According to this invention, carbon or a material that can be subsequently converted to carbon is pre-formed into a shape. The pre-formed carbonaceous material is treated with a sol which comprises a metal oxide precursor that subsequently can be converted to a metal oxide. This results in the deposition of the metal oxide precursor into the pre-formed carbonaceous material. The pre-formed and to said United States patent application, including any continuations and divisions thereof, and any substitute applications therefor and all right, title and interest in and to any United States patent which may issue thereon and any reissues of the same; and we hereby authorize and request competent authorities to grant and issue any and all patents on said invention in the United States to the said PHILIP MORRIS INCORPORATED as the assignee of the entire United States interest therein.